Preparation of pure myristic alcohol



Unit d S ate Paten fi ice invention'relatcs to methodsof preparing purew; coho], and about oleic alcohol.

n-tetradecanol or myristic alcohol from residual products derived fromalkaline cracking of castor "oil. N-tetrade canol,otherwise calledmyris'tic alcohol, is a l4-carbon aliphatic alcohol possessing valuablecommercial prop erties. The'compound is especially'used in thepreparation of :germicides, emulsifiers, detergent and cosmeticcompositions.

conventional process of preparing sebacic acid, a commercial producthaving a wide range of uses and manufactured in large quantitiesinvolves splitting or cracking castor oil at high temperature in thepresence of concentrated caustic alkali solutions. During the alkalinesplitting reaction, the I'll-carbon chain of the ricinoleic acidcontained in a concentration of about 85% in the castor oil splits intotwo segments respectively'containing 10 and 8 carbon atoms, and hydrogengas is evolved. The IO-carbon fraction'comprises sebacic acid while the8- earbon fraction essentially comprises octanol-Z and octanone-Z. e

In the alkaline splitting of castor oil the octyl derivatives arereadily separable by entrainment with water vapour. The splittingprocess can be carried out at ordinary pressures or at a limitedpressure with a continuous distillation of the octanol-Z and octanone-2together with part of the water supplied in the alkaline lye.Alternatively the reaction may be conducted in a sealed reactor with afinal distillation of the octyl products and part of the water, 'whilethe hydrogen evolved in the reaction is allowed to expand.

The octanol-Z and octanone-Z in pure form can easily be separated inpure form by known rectification-distillation techniques. At the end ofthe distillation process there remains a residue comprising fattycompounds representing about 2 to 3% of the initial castor oil used.This residue is believed to result from the non ricinoleic fractions ofthe initial castor oil which failed to split into sebacic acid and octylcompounds.

This fatty residue, which may for convenience be described as a mixtureof crude sebacic aliphatic alcohols, is a complex mixture and while itsprecise composition is not known, the hydroxyl index, saponificationindex, and iodine index thereof can be readily determined. When it isattempted to resolve the mixture into its constituents by distillationin vacuo, various ill-defined fractions are obtained with rather pooryields, partial de-composition ensues and tarry compounds form. Inpractice, such mixtures of crude sebacic fatty alcohols have heretoforebeen regarded as commercially valueless by-products.

We have now made the surprising discovery that by a relatively simpleprocedure to be described, such crude sebacic fatty alcohols can beconverted into valuable compolmds having definite chemical composition.The process essentially involves treating the mixtures with superheatedsteam in a temperature range of about 150- 250 C. in the presence of anamount of caustic alkali not less than that corresponding to thesaponification in- I Patented July 28, 1 959 dex of the mixture beingtreated. Fatty alcohols are thus produced which are separable bydistillation into pure constituents. The end products comprise a smallqnantity of octanol-2, while at least 80% of the resulting mixturecomprise pure n-tetradecanol'or myristic a1- ..fIhe result justdescribed is unexpected for several reasons. First, the desirability ofperforming a further alkaline saponification step was hardly to bepredicted since the starting materia-ls themselves originated the highlyalkaline medium present in the sebacic splitting reaction Then, thefac't that the bulk of the reaction product is myristic alcohol wastotally unexpected, since no l4-carbon aliphatic chains were ever beforerecognized as being present in the composition of castor oil.

As already mentioned, pure myristic alcohol has considerable commercialvaluesince it is used .in the manufacture of highly surface-active fattyalcohol sulfates, in the preparation of quaternary ammonium salts havinggermicidal properties, non-ionic emulsifiers and detergents, cosmeticsand other commodities. An interesting point is that, within the wholeseries of surface-active agents derivable from aliphatic chains, theoptimum average properties are found to be achieved where thechainincludes l4'carbon atoms. Y

'Oleic alcohol which is a by-product of the process is likewise valuablein the manufacture of sulfonates and non ionic derivatives. 1 7 'Some'examples will now be described as illustrations of the invention. Partsby weight and parts by volume are related as grams to cubic centimeters.

. Example 1 1st srep.; -'0ctan0l-2 and octanone-Z are first preparedbythe followin conventional process.

An oblong stainless steel-lined autoclave is used to perform acontinuous alkaline splitting of castor oil, by pumping into the bottomof the autoclave parts castor oil per parts soda lye at a concentrationof 40% by weight. The autoclave is heated to 300 C. and the reactionmixture is withdrawn from the top of the autoclave and allowed toexpand. The gaseous phase resulting from the expansion is passed into acooler and condenses into a lighter organic phase and a heavier phaseessentially containing water.

The supernatent organic phase is dried and distilled. A mixture isobtained comprising octanol-2 and octanone-Z boiling at 172-178 C. atatmospheric pressure. The octanone passes as a head fraction and pureoctanol- 2 is collected at 177178 C. The heavy remaining residualfractions are waxlike, brown, and represent about 2 to 3% of the initialcastor oil. The residual mixture is found to have the followingcharacteristics:

Saponification index 66 Hydroxyl index 169 Iodine index 30 2nd step-Thewaxlike residual mixture which comprises the crude sebacic fatty alcohomixture mentioned previously, is now distilled in a vacuum of about 17mm. Hg. In the temperature range from 85 to 195 C. no definite fractionis found to distill. 'In the 85 to 125 C. range a fraction is obtainedhaving a saponification index 6 and comprising impure octanol 2.Subsequent fractions obtained at increasing distillation temperaturesare found to possess the following saponification indices: 125-160" C.,8.1. 28; 180 C., 8.1. 10; and 180-195 C., 8.1. 70. A dark residueremains which breaks down rapidly and has a saponification index of 131.This residue represents about 40% of the crude sebacic fatty alcoholsinitially present.

It is noted that in the step just described which is a conventionalfractional distillation, none of the fractions produced is a purealcohol.

Example 2 The crude sebacic fatty alcohol mixture obtained as at the endof the first step in Example 1, is. treated in in accordance with theinvention. For this purpose the mixture is placed in a steel, oil-firedboiler provided with a dipper pipe connected with a source ofsuperheated steam at 3 kg./sq. cm. pressure (about 110 C.) and providedwith an agitator. The boiler is connected to a condenser provided withcold water circulation. A quantity of soda lye at a concentration of 30%by Weight is added, corresponding to the saponification index of themixture plus an excess of about 'The mixture is then heated to 220 C.with agitation and steam is delivered through the dipper pipe. Mixedwater and. fatty alcohol vapours evolve which condense, and the organicfraction is separated from the heavier water fraction.

The gradual entrainment of the fatty alcohols serves in itself as a kindof rectifying operation. Thus the vapours discharged into the condenserare initially charged essentially with octanol-Z, and the temperature inthe condenser is at that time about 130 C. As the condenser temperaturerises above 170 C., the condensate partly sets and now contains heavyfatty alcohols. The entrainment is continued until a point Where thecondensed Water no longer carries any alcohol with it. At this time thetemperature in the vapour is about 210 C. The boiler contains a residueof soda soap. This results from the sodic fraction of the esters presentin the initial sebacic fatty alcohol mixture and represents about 25% ofthe starting material introduced.

The alcohols entrained by the steam represent about 75% by weight of theinitial content. Their sponification index is zero and they areseparated by fractional distillation, first at ordinary pressure then invacuo. Three distinctly separate ranges of distillation are observed:

177-178 C. at ordinary pressure,

nol-Z.

166-168 C. at 15 mm. Hg, corresponding to n-tetradeca- 185-187 C. at 15mm. Hg, corresponding to oleic acid.

corresponding to octa- The n-tetradecanol obtained by this processrepresents of the crude sebacic fatty alcohols introduced, and of thepurified alcohols recovered. Its character- Its melting point is notaltered when mixed with a batch of control myristic alcohol, and it hasthe same analytic distillation curve, .whether.alone or in admixturewith the control.

What we claim is:

1. The method of preparing pure myristic alcohol, comprising,alkali-splitting castor oil, distilling the. octanol-2 and octanone-Zfrom the residue of the alkali-splitting reaction, entraining theresidue stripped ofoctanol-Z and octanone-2 with superheated steam atabout to 250? C. in the presence of alkali lye in an amount not lessthan that corresponding to the saponification index .of said residue,and recovering pure myristic alcohol from the distillation condensate.

2. The method claimed inclaim 1, wherein the entrainment is performedfractionally, so as to yield separate fractions comprising pure.octanol-Z, pure myristic alcohol and pure oleic alcohol. 7

References Cited in the file of this patent:

1. THE METHOD OF PREPARING PURE MYRISTIC ALCOHOL, COMPRISING,ALKALI-SPLITTING CASTOR OIL, DISTILLING THE OCTANOL-2 AND OCTANONE-2FROM THE RESIDUE OF THE ALKALI-SPLITTING REACTION, ENTRAINING THERESIDUE STRIPPED OF OCTANOL-2 AND OCTANONE-2 WITH SUPERHEATED STREAM ATABOUT 150 TO 250* C, IN THE PRESENCE OF ALKALI LYE IN AN AMOUNT NOT LESSTHAN THAT CORRESPONDING TO THE SAPONIFICATION INDEX OF SAID RESIDUE ANDRECOVERING PURE MYRISTIC ALCOHOL FROM THE DISTILLATION CONSENSATE.